1. Field of the Invention
The present invention is directed generally to scientific laboratory analytical equipment, and more particularly, to the combination of Chromatography Systems and Mass Spectrometers.
2. Background of the Related Art
Scientific laboratories commonly need to analyse samples by the use of Chromatography in order to separate different constituents within the samples. Once the samples have been separated, they may need further analysis in order to identify what the different constituents are. Normally the most effective way of performing the analysis of the separated constituents is the use of mass spectrometers.
Chromatography can be performed either on gaseous samples or on liquid samples. However, the apparatus required to perform Liquid Chromatography and Gas Chromatography are rather different, so much so that different machines are required to perform the different analyses.
Mass spectrometers can be used to measure the mass of ions and analyse the structure of these ions, by studying fragmentation of the ions that may occur within the mass spectrometer. Chromatography systems typically produce molecules rather than ions, so the mass spectrometer needs to produce ions from the molecules that are delivered to it. This typically is performed in an ion source. There are many ways of ionizing the molecules that are injected into an ion source. Atmospheric Pressure Chemical Ionisation [APCI] is one of these methods. In this method, the molecules are sprayed into an ion source chamber and the spray is subjected to a corona discharge that creates ions.
APCI is a desirable fragmentation technique because it typically produces singly charged ions, and so the results of the analysis are easier to interpret. Furthermore APCI is a method of ionization that is possible to use for samples that are both liquid and gaseous.
Mass Spectrometers are precise instruments, and so are expensive and delicate. Until recently, they have always been specifically designed for one of LCMS or GCMS and not for interchangable use. In the past also instruments have been designed to swap between GCMS and LCMS. However, the changeover has been time consuming and often the dual instruments compromised the performance on one or the other of the two techniques. This is especially true for Vacuum GCMS systems utilizing Electron Impact Ionization. The advantage of using APCI is that both LCMS and GCMS are operated at the same pressure and there is no need to change the MS other than to put an ion chamber on in place of a cone gas nozzle.
An attempt to provide a dual source mass spectrometry system comprises a mass spectrometer that has an ion source capable of being used for either LCMS or GCMS. However the design of the source is such that both an LCMS interface probe and a GCMS interface probe are permanently connected to an API source housing. This arrangement is an improvement over the use of separate LCMS and GCMS machines but is inefficient, and so cannot easily identify small quantities of analytes that may be present in the sample.
It would therefore be desirable to produce a Mass Spectrometer that is capable of efficiently analysing the output of either liquid or gas chromatography systems with easy transfer between the two different inputs, and with easy and minimal alterations required as now provided by the present invention.
It is envisaged that the dual source mass spectrometry system of the present invention has applications for example in synthetics confirmation and impurity profiling, natural products research, and in the fields of flavours and fragrances, nutraceuticals, petrochemicals, metabolomics, environmental screening, pesticide residue analysis and some forensic applications. The combination of LCMS and GCMS allows a wider range of compounds to be analyzed on a single instrument platform.